Modulation of driving forces fo UiO-66 analog adsorbents by decoration with amino functional groups: Superior adsorption of hazardous dyes

Metal-organic frameworks (MOFs) are promising adsorbents that can be improved for practical applications by functionalization. Herein, we report UiO-66-NH2, an amino-modified MOF with a superior toxic dye adsorption performance. Uncoordinated -NH2 groups were successfully introduced into the UiO-66 framework to modulate the adsorption driving forces between toxic organic dyes and the UiO-66-NH2 adsorbent by varying the molar ratios of the organic linkers 2-aminoterephthalic acid and terephthalic acid (H2BDC-NH2:H2BDC). The adsorption uptakes of the UiO-66-NH2 adsorbent with a H2BDC-NH2:H2BDC of 1:9 were 538.2 mg g(-1) for methyl orange and 224.2 mg g(-1) for methylene blue, which were respectively 207.2% and 815.1% higher than those of undecorated UiO-66. The adsorption behavior of the modified UiO-66-NH2 adsorbent is controlled by the synergistic interplay between pi-pi interactions, electrostatic attraction/repulsion, and hydrogen bonding, as well as the pore volume of the adsorbent. (C) 2020 Elsevier B.V. All rights reserved.